1. Field of the Invention
The present invention relates to a method of processing a call to an unregistered user in a 3rd Generation-General Packet Radio Service (3G-GPRS) based Wireless Local Area Network (WLAN) for Voice over Internet Protocol (VoIP) based on a Session Initiation Protocol (SIP).
2. Description of the Related Art
In order to take an SIP based VoIP service in a conventional WLAN environment, a mobile node (MN) must always be connected to an IP and complete SIP registration to connect a call from another MN. In this situation, due to nonexistence of location based service in the WLAN environment, it is difficult to detect the location of a MN. In addition, every MN occupies resources for IP connection to make SIP registration in a network.